The include/telkin/Assembly.h file includes helpers for working with inline assembly in C++ source files.

Assembly Function Declaration

The tAssembly macro can be used to define the body of a function using only PowerPC assembly instructions.

#define TELKIN_REGISTERS
#include <telkin/Assembly.h>
 
void func() tAssembly(
    li r3, 0xFF;
    blr;
)

Defining the TELKIN_REGISTERS macro will generate lots of macros that map register names such as r3 to the underlying format that is expected by the compiler r3. Since these identifiers are very short and may cause conflicts, you may globally opt-out of the macro by defining TELKIN_NO_REGISTERS through the compiler flags.

If a conflict is caused within a file that also needs the register definitions, you may include UndefineRegisters.h and DefineRegisters.h an unlimited number of times.

Register Preservation

Applying the tRegSave attribute onto a C++ function definition will cause every single volatile register to be saved and restored at the end of the function, so that mid-function hooks do not corrupt any state. If the function does return a value (which corresponds to r3) then r3 will be omitted from the restorations and thus will be allowed to change.

There are also macros available for use in assembly functions:

tSaveVolatileRegisters: Saves r0, r3-r12, CR, CTR, and LR to the stack
tRestoreVolatileRegisters: Restores r0, r3-12, CR, CTR, and LR from the stack
tSaveLR: Saves LR to the stack (through clobbering r2)
tRestoreLR: Restores LR from the stack (through clobbering r2)

Compile-time Assembler

The tk::ppc namespace provides a set of consteval functions which return assembled machine code u32s for various PowerPC instructions. This is useful alongside patch hooks (specifically tPatch32u) to replace an instruction in-line within a function.

Telkin